JP5481368B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus and an image forming apparatus that read an image using a plurality of light emitting elements.

  With the recent increase in the amount of light emitted from white LEDs (Light Emitting Diodes), white LEDs have begun to be used as light sources for copiers and scanners using a condensing sensor (CCD or CMOS image sensor). In general, since a condensing sensor requires a large amount of light, a necessary amount of light is generated by lighting a plurality of white LEDs side by side in the reading direction.

  For example, as shown in FIG. 8, conventionally, a light beam (dotted line in the figure) irradiated from such a light source is scattered on the surface of the original placed on the contact glass, and the scattered light (solid line in the figure). A part of the lens is guided to the condensing lens by three reflecting mirrors, condensed on an image sensor such as a CCD by the condensing lens, and the collected light is photoelectrically converted by the image sensor to correspond to the reading position. Document reading processing for forming image data to be performed is performed. Then, by repeating the series of document reading processes while moving the light source in the sub-scanning direction, image data corresponding to the entire document is formed, and reading of one document is completed.

  For example, the following Patent Document 1 describes a light source of a reading optical system configured by a plurality of point light sources arranged in parallel with a main scanning direction that is a reading direction of a line sensor (image sensor). A technique for reading an original in units of one line in the main scanning direction with a light source is described.

JP 2002-314760 A

  However, for example, as shown in FIG. 8, when a document placed parallel to the contact glass surface is read by the document reading process described above, a part of the irradiation light scattered at a uniform rate on the document surface is obtained. As shown in FIG. 9, when a curled document such as a binding portion of the original document is read by the above-described document reading process as shown in FIG. When the irradiation light (dotted line in the figure) is reflected on the original surface (solid line in the figure), the angle formed by the original light and the light from the light source is the same as the angle formed by the original light and the reflected light. A quantity of specularly reflected light may enter the reflection mirror and enter the image sensor.

  Therefore, when reading such a line, the scattered light that would otherwise be incident on the image sensor at a uniform rate is incident on the image sensor at a rate that depends on the large amount of light from the specularly reflected light. There is a possibility that the image generated by the incidence of the reflected light at a position facing the position in the main scanning direction of the light emitting element constituting the light source becomes a dotted white spot (density unevenness). When a document placed parallel to the contact glass surface is read by the above document reading process, even if specular reflection light may be incident on the reflection mirror as described above, it is parallel to the contact glass surface. If density unevenness also occurred when the white reference plate used for the mounted shading correction was read, the density unevenness could be eliminated by the shading correction.

  An image including such density unevenness has a different sense of discomfort to the viewer depending on the density difference and the number of density unevenness, but the bright spot is particularly noticeable when the bright spot portions are scattered brightly. In order to correct the portion, it has been desired to first specify the positions of scattered bright spot portions.

  SUMMARY An advantage of some aspects of the invention is that it provides an image reading apparatus capable of specifying a position where density unevenness occurs when a document is read. It is another object of the present invention to provide an image forming apparatus including such an image reading apparatus.

The invention according to claim 1 is a document table for placing a document;
A light source unit that includes a plurality of light emitting elements arranged in a main scanning direction, and that irradiates a document placed on the document table with lighting light of the plurality of light emitting elements;
The reflected light reflected from the original when the lighting light is irradiated by the light source unit to the reading target line which is one line in the main scanning direction of the original to be read in the original, and the received reflected light is received. A light receiving unit that converts the image data of the line to be read;
A light source controller that controls turning on and off of the plurality of light emitting elements;
When all the plurality of light emitting elements are turned on by the light source control unit, all lighting read data that is the image data of the reading target line converted by the light receiving unit, and the light source control unit that is turned on Each of the main scanning directions in the thinning-on reading data which is the image data of the reading target line converted by the light receiving unit when a predetermined number of the light emitting elements adjacent to the light emitting elements are turned off. A difference between pixel data is calculated, and when the difference value larger than a predetermined first threshold difference value exists among the calculated difference values, a predetermined value smaller than the first threshold difference value is determined. The pixel data corresponding to the difference value smaller than the second threshold difference value and the image indicated by the pixel data corresponding to the difference value larger than the first threshold difference value And uneven density specifying unit configured to specify a density unevenness occurring position in the reading target line,
An image reading apparatus.

According to a third aspect of the present invention, there is provided the image reading device according to the first or second aspect,
An image forming unit that forms an image on a recording medium based on an image signal obtained by a reading operation of the image reading device;
An image forming apparatus.

  In these inventions, it is possible to specify the density unevenness occurrence positions scattered in the image data generated by reading the reading target line of the document by the light source unit and the light receiving unit. For this reason, for example, it is possible to appropriately specify a pixel to be subjected to a correction process that reduces the appearance of density unevenness, for example, by replacing pixel data of the specified density unevenness occurrence position with pixel data of surrounding pixels. become.

The invention according to claim 2 is the image reading apparatus according to claim 1,
A document type receiving unit that receives an input of the document type;
The density unevenness specifying unit performs the process of specifying the density unevenness occurrence position only when the document type received by the document type receiving unit is the original document.

  According to the present invention, it is possible to specify the density unevenness occurrence position that occurs in the binding portion of the original that has a non-planar original surface, which is suitable for reading the original.

  According to the present invention, it is possible to provide an image reading apparatus capable of specifying the occurrence position of density unevenness that occurs when reading a document. It is also possible to provide an image forming apparatus provided with such an image reading apparatus.

1 is a schematic cross-sectional view showing a multifunction machine as an example of an image forming apparatus according to the present invention. 1 is a schematic sectional view showing an example of an image reading apparatus according to the present invention. The block diagram which shows an example of the light source part which concerns on this invention. FIG. 3 is a block diagram illustrating an example of an image reading circuit. Explanatory drawing which shows an example of all lighting reading data and thinning lighting reading data. The flowchart which shows an example of the operation | movement which pinpoints a density nonuniformity generation | occurrence | production position. The block diagram which shows an example different from FIG. 3 of the light source part which concerns on this invention. FIG. 10 is an explanatory diagram illustrating an example of a conventional document reading operation. FIG. 3 is an explanatory diagram illustrating an example of density unevenness that occurs when a document is read.

  Hereinafter, a multifunction peripheral as an example of an image forming apparatus according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the multifunction machine 1 has a plurality of functions such as a copy, a printer, a scanner, and a facsimile, and has a main body 2 and a stack tray 3 disposed on the left side of the main body 2. An operation unit 36 for a user to input various operation commands and the like, an image reading unit 4 disposed above the main body unit 2, and a document feeding unit disposed above the image reading unit 4. And 5.

  The main body 2 includes a plurality of paper feed cassettes 23, a paper feed roller 24 that feeds recording paper from the paper feed cassette 23 one by one and transports it to the image forming unit 25, and a recording paper transported from the paper feed cassette 23. And an image forming unit 25 for forming an image.

  The image forming unit 25 forms a toner image on the photosensitive drum 26 and an optical unit 27 that outputs laser light or the like based on an image signal acquired by the image reading unit 4 to be described later to expose the photosensitive drum 26. A developing unit 28, a transfer unit 29 for transferring the toner image on the photosensitive drum 26 to the recording paper, and a pair of rollers 30 and 31 for fixing the toner image to the recording paper by heating the recording paper to which the toner image has been transferred. And a pair of conveyance rollers 34 and 35 that are provided in the sheet conveyance path in the image forming unit 25 and convey the recording sheet to the stack tray 3 or the discharge tray 33.

  When forming images on both sides of the recording paper, the image forming unit 25 forms an image on one side of the recording paper, and then the recording paper is nipped between the pair of conveying rollers 30 and 31 on the discharge tray 33 side. State. In this state, the pair of conveying rollers 30 and 31 are reversed to switch back the recording sheet, and the recording sheet is sent to the sheet conveying path 32 and conveyed again to the upstream area of the image forming unit 25. After the image is formed, the recording paper is discharged to the stack tray 3 or the discharge tray 33.

  The operation unit 36 displays a start key 361 for a user to input a print execution instruction, a numeric keypad 362 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 363 including a liquid crystal display having a touch panel function, a reset key 364 for resetting setting contents set on the display unit 363, and a stop key 365 for stopping a printing (image forming) operation being executed. A function switching key 366 for switching between a copy function, a printer function, a scanner function, and a facsimile function.

  As shown in FIG. 2, the document feeder 5 includes a document tray 51, a sheet feed roller 52, a transport drum 53, a sheet discharge roller 54, and a sheet discharge tray 55, and an ADF (Auto Document Feeder). Configure.

  The document tray 51 is a place where the document is placed. The documents placed on the document tray 51 are taken one by one by the paper feed roller 52 and conveyed to the conveyance drum 53. The document that has passed through the transport drum 53 is discharged to a discharge tray 55 by a discharge roller 54.

  The image reading unit 4 optically acquires an image of a document and outputs an image signal. As shown in FIG. 2, the image reading unit 4 is a flat bed contact glass 411 as a document table according to the present invention. The light source 42 includes a light source 42, a first mirror 431, a second mirror 432, a third mirror 433, a first carriage 46, a second carriage 47, an imaging lens 48, and a CCD (Charge Coupled Device) 49. In addition to the CCD, a CMOS (Complementary Metal Oxide Semiconductor) image sensor may be used.

  The contact glass 411 is a place where a document is placed. The light source 42 and the first mirror 431 are supported by the first carriage 46, and the second mirror 432 and the third mirror 433 are supported by the second carriage 47.

  In this configuration, as a document image reading method using the image reading unit 4 and the document feeding unit 5, the image reading unit 4 reads a document placed on the contact glass 411, and the document is ADF. There are two types of original image reading methods in the ADF reading mode in which the original is read in the middle of the transfer and the original is read during the conveyance.

  In the flat bed reading mode, the light source 42 irradiates a reading target line that is one line in the main scanning direction of the reading target in the document placed on the contact glass 411, and reflected light from the reading target line is reflected by the first mirror 431. The second mirror 432 and the third mirror 433 are reflected in this order and enter the imaging lens 48. Light incident on the imaging lens 48 is imaged by photoelectric conversion on the light receiving surface of the CCD 49.

  The CCD 49 is a one-dimensional image sensor, which simultaneously processes an image of a document for one line and outputs an image signal. When the reading for one line is completed, the first carriage 46 and the second carriage 47 are moved in a direction (sub-scanning direction, arrow Y direction) perpendicular to the main scanning direction (direction perpendicular to the paper surface) of the document. The line is read.

  On the other hand, in the ADF reading mode, the originals placed on the paper supply tray 51 are taken in one by one by the paper supply roller 52, and the originals are provided on the conveyance path from the conveyance drum 53 to the paper discharge tray 55. When passing through a gap between 410 and the guide plate 59, the light source 42 irradiates the reading target line of the document through the reading window 410. The reflected light from the reading target line is reflected by the first mirror 431, the second mirror 432, and the third mirror 433 in this order and enters the imaging lens 48, and the light incident on the imaging lens 48 is the light receiving surface of the CCD 49. The image is formed by photoelectric conversion. Subsequently, the document is conveyed by the document feeder 5 and the next line is read.

  In the following description, it is assumed that the document image reading method is the flatbed reading mode.

  As described above, in the image reading unit 4, the reflected light from the original is guided to the CCD 49 by the optical system to obtain an image signal. However, in order to correct individual differences in characteristics of the CCD 49 and uneven illuminance due to the light source 42, Shading correction is performed.

  In this shading correction, the white light source 42 illuminates the white reference plate 412 previously placed parallel to the contact glass 411 surface and the reflected light is received by the CCD 49 before reading the document. Is a process of correcting the density unevenness of the image signal using the black reference data obtained in a state where the light is shielded.

  As shown in FIG. 3, the light source 42 includes light emitting element groups 6 and 7 formed by connecting four white LEDs as an example of the light emitting element according to the present invention in series. The number of white LEDs provided in each light emitting element group (4 in this example) and the number of light emitting element groups (2 in this example) are merely examples, and are not intended to be limited thereto.

  The light emitting element group 6 includes white LEDs 61 to 64 connected in series, and is connected between the A terminal of the constant current drive circuit 80 and the power source. The light emitting element group 7 includes white LEDs 71 to 74 connected in series, and is connected between the B terminal of the constant current drive circuit 80 and the power source.

  The white LEDs of the light emitting element groups 6 and 7 are alternately arranged in the main scanning direction (arrow X direction) of the document for each light emitting element group. For example, as shown in FIG. 3, the white LED 61 of the light emitting element group 6, the white LED 71 of the light emitting element group 7, the white LED 62 of the light emitting element group 6, and the light emitting element group 7 along the main scanning direction of the document from the left side of the page. The white LEDs 72 and the white LEDs 63 of the light emitting element group 6 are arranged in this order.

  The constant current drive circuit 80 takes in a current adjustment signal output from a light source control unit 94, which will be described later, and supplies and blocks a constant current to the light emitting element groups 6 and 7 according to the instruction content indicated by the current adjustment signal. , 7 are driven and stopped. As a result, the white LEDs provided in the light emitting element groups 6 and 7 are turned on and off, and the lighting light of the white LEDs is applied to the document.

  Next, an image reading circuit that controls an image reading operation in the multifunction machine 1 will be described. As shown in FIG. 4, the image reading circuit 9 includes a CPU 91, a RAM 92, a ROM 93, a light source control unit 94, a drive control unit 95, an operation unit 36, an A / D conversion unit 97, and a shading correction unit. 98, a density unevenness specifying unit 90, and an image processing unit 99, which are communicably connected to each other via a bus BUS.

  The CPU 91 is composed of a control mechanism that controls overall operation of the multifunction machine 1, and acquires white reference data and black reference data for image reading operation and shading correction of the image by the image reading unit 4 and the document feeding unit 5. It is also in charge of controlling the operation. The CPU 91 controls the operation of the multifunction device 1 according to an operation control program stored in the ROM 93 or a hard disk (HDD) not shown.

  The RAM 92 is a storage mechanism used as a work area during operation control by the CPU 91 in accordance with the operation control program. The ROM 93 stores the operation control program, a first threshold difference value, a second threshold difference value, and the like used in an operation of specifying a density unevenness occurrence position in a density unevenness specifying unit 90 described later.

  The light source control unit 94 outputs a control signal (current adjustment signal) instructing to supply a constant current to the light emitting element groups 6 and 7 to be driven to the constant current drive circuit 80 (FIG. 3), whereby the light source The lighting and extinguishing operations of 42 are controlled.

  The drive control unit 95 controls the operation of drive mechanisms such as the paper feed roller 52 and the paper discharge roller 54 of the document feed unit 5 and the first carriage 46 and the second carriage 47 of the image reading unit 4.

  As described above, the operation unit 36 receives input of various operation commands such as a copy operation start instruction from the user.

  The A / D conversion unit 97 converts an analog image signal output from the CCD 49 of the image reading unit 4 into a digital image signal (image data), and stores the image data in the RAM 92.

  The shading correction unit 98 performs shading correction on the image data stored in the RAM 92 by using the white reference data and the black reference data acquired by the image reading unit 4, the document feeding unit 5, and the CPU 91 before reading the document. The corrected image data is stored in the RAM 92. That is, the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 constitute an example of a light receiving unit according to the present invention.

  The density unevenness specifying unit 90 includes the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 when all the white LEDs 61 to 64 and 71 to 74 provided in the light source 42 are turned on by the light source control unit 94. The all-on reading data (for example, the solid line portion in FIG. 5A) that is image data of the reading target line stored in the RAM 92 and a white LED that is lighted by the light source control unit 94 is set in advance. When the number of white LEDs (one in the figure) is turned off, the thinning light that is the image data of the line to be read stored in the RAM 92 via the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 is turned on. The difference between the read data (for example, the solid line portion in FIG. 5B) and the pixel data in the main scanning direction (corresponding to ΔL in FIG. 5B) Calculated to.

  Then, if there is a difference value that is larger than the predetermined first threshold difference value among the calculated difference values, the density unevenness specifying unit 90 selects the pixel indicated by the pixel data corresponding to the difference value. It is specified as the density unevenness occurrence position in the reading target line. The first threshold difference value is determined in advance based on an experimental value obtained by a test operation or the like before product shipment, and is stored in the ROM 93.

  That is, for example, when a curled line such as a binding portion of the original is read as a reading target line, when all the white LEDs are turned on, the lighting light from any of the white LEDs is reflected by the reading target line. In addition, depending on the reading target line, a large amount of specularly reflected light is incident on the CCD 49 with the same angle between the original surface and the irradiation light from the light source and the same angle between the original surface and the reflected light. However, if a predetermined number of white LEDs are thinned and turned on, any one of the white LEDs may be turned off. In this case, regular reflection light that should be incident is not incident on the CCD 49.

  In view of this, the density unevenness specifying unit 90 includes pixel data acquired via the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 in which the calculated difference value is larger than a predetermined first threshold difference value. When a large value corresponding to the amount of specularly reflected light that is close to the allowable maximum value is indicated, the pixel indicated by the pixel data corresponding to the difference value is specified as the density unevenness occurrence position.

  For example, in the example illustrated in FIG. 5, the density unevenness specifying unit 90 is a pixel at a position facing the white LEDs 71 to 74, and a difference value of each pixel data between all lighting read data and thinned lighting reading data is determined in advance. Therefore, it is determined that the pixel value is larger than the first threshold difference value, and the pixel at the position facing the white LEDs 71 to 74 is specified as the density unevenness occurrence position.

  In addition, when there is a difference value larger than the first threshold difference value among the calculated difference values, the density unevenness specifying unit 90 preliminarily smaller than the first threshold difference value among the calculated difference values. A pixel indicated by pixel data corresponding to a difference value smaller than the determined second threshold difference value is specified as a density unevenness occurrence position in the reading target line. The second threshold difference value is determined in advance based on an experimental value obtained by a test operation or the like before product shipment, and stored in the ROM 93, similarly to the first threshold difference value.

  That is, for example, when a curled line such as a binding portion of the original is read as a reading target line, when all the white LEDs are turned on, the lighting light from any of the white LEDs is reflected by the reading target line. Are regularly incident on the CCD 49. Further, even if a predetermined number of white LEDs are thinned and turned on, any one of the white LEDs may be turned on. In this case, the regular reflection light is incident on the CCD 49.

  In view of this, the density unevenness specifying unit 90 includes pixel data acquired via the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 in which the calculated difference value is smaller than a predetermined second threshold difference value. Even when a small value that is a difference value between large values corresponding to the amount of specularly reflected light that is close to the maximum allowable value is indicated, the pixel indicated by the pixel data corresponding to the difference value is specified as the density unevenness occurrence position. ing.

  For example, in the example shown in FIG. 5, the density unevenness specifying unit 90, as described above, determines the difference value of each pixel data between the all lighting reading data and the thinning lighting reading data from a predetermined first threshold difference value. Since there is a pixel at a position opposite to the white LEDs 71 to 74, the difference value of each pixel data in the all lighting reading data and the thinning lighting reading data is smaller than a predetermined second threshold difference value. A pixel at a position facing the white LEDs 61 to 64 is specified as a density unevenness occurrence position.

  On the other hand, when the regular reflection light reflected by the document is not incident on the CCD 49, for example, when a line parallel to the contact glass 411 is read as a reading target line, all white LEDs are turned on. Since the shading correction by the shading correction unit 98 is performed both when the predetermined number of white LEDs are thinned and turned on, each pixel data in the image data after the shading correction is substantially equal. That is, in this case, the density unevenness specifying unit 90 does not include pixel data that is larger than a predetermined first threshold difference value among the difference values of the pixel data in the all-lighting reading data and the thinned lighting reading data. Therefore, the position where density unevenness occurs is not specified.

  Then, when the density unevenness specifying unit 90 specifies the density unevenness occurrence position, for example, among all lighting read data, correction is performed to darken only the pixel data of the pixel indicated by the specified density unevenness occurrence position. Alternatively, the pixel data of the pixel is replaced with the pixel data of the peripheral pixel of the pixel, and the pixel data at the density unevenness occurrence position in the all lighting read data is corrected, and the corrected image data is stored in the RAM 92.

  The image processing unit 99 performs correction processing such as level correction and gamma correction, compression or expansion processing, enlargement or reduction processing, and the like on the image data corrected through the density unevenness specifying unit 90 stored in the RAM 92. Various image processing is performed.

  That is, the image reading unit 4, the document feeding unit 5, the operation unit 36, and the image reading circuit 9 are provided to constitute an example of the image reading apparatus according to the present invention.

  Hereinafter, an operation of specifying the density unevenness occurrence position in the density unevenness specifying unit 90 will be described in detail. As shown in FIG. 6, when an execution instruction for a copy function, a scanner function, or the like is received by the operation unit 36 and execution of an image reading process for a document using the image reading unit 4 and the document feeding unit 5 is started, The density unevenness specifying unit 90 sends an instruction to turn on all the white LEDs 61 to 64 and 71 to 74 to the light source control unit 94 (S1), and the lighting lights of the white LEDs 61 to 64 and 71 to 74 are applied to the original according to the instructions. Reflected light reflected from the reading target line when it is irradiated to the reading target line is received by the CCD 49, and output from the CCD 49, the A / D conversion unit 97, and the shading correction unit 98. The image data is stored in the RAM 92 as all lighting read data (S2).

  Next, the density unevenness specifying unit 90 turns on the white LEDs 61 to 64 provided in the light emitting element group 6 and turns off one white LED adjacent to the white LEDs 61 to 64. An instruction to turn off the provided white LEDs 71 to 74 is sent to the light source control unit 94 (S3), and in accordance with the instructions, the lighting light of the white LEDs 61 to 64 is applied to the same reading target line as the reading target line in step S2. At this time, the reflected light reflected from the reading target line is received by the CCD 49, and the image data of the reading target line output through the CCD 49, the A / D conversion unit 97, and the shading correction unit 98 is thinned out and read data. Is stored in the RAM 92 (S4).

  Then, the density unevenness specifying unit 90 calculates the difference between the pixel data in the main scanning direction between the all-lighting reading data and the thinned lighting reading data stored in the RAM 92 and stores the difference in the RAM 92 (S5). It is determined whether or not the difference value is larger than a predetermined first threshold difference value stored in the ROM 93 (S6), and if the calculated difference value is larger than a predetermined first threshold difference value. If it is determined (S6; YES), the coordinates of the pixel indicated by the pixel data corresponding to the calculated difference value are stored in the RAM 92 as the density unevenness occurrence position (S7).

  Then, when the density unevenness specifying unit 90 ends the determination process of step S6 for all the pixel data in the all lighting read data and the thinned light reading data stored in the RAM 92 (S8; YES), the density unevenness occurs in the RAM 92. It is determined whether or not the coordinates of the pixel as the position are stored (S9).

  Here, when the density unevenness specifying unit 90 determines that the coordinates of the pixel as the density unevenness occurrence position are stored in the RAM 92 (S9; YES), it further thins out all the lighting reading data stored in the RAM 92 in step S5. It is determined whether or not the difference value of each pixel data in the lighting read data is smaller than a predetermined second threshold difference value stored in the ROM 93 (S10), and the difference value is determined in advance. When it is determined that the difference is smaller than the threshold difference value (S10; YES), the coordinates of the pixel indicated by the pixel data corresponding to the difference value are stored in the RAM 92 as the density unevenness occurrence position (S11).

  Then, when the density unevenness specifying unit 90 completes the determination process of step S10 for all the difference values of the pixel data in the all-lighting reading data and the thinned lighting reading data stored in the RAM 92 (S12; YES), Of all the lighting data, correction is performed to darken only the pixel data of the pixel indicated by the coordinates stored in the RAM 92 as the density unevenness occurrence position in step S7 or step S12, or the pixel data of the peripheral pixel of the pixel Image data obtained by correcting the pixel data of the density unevenness generation position is generated by replacing the pixel data of the pixels (S13).

  Next, the density unevenness specifying unit 90 stores the image data corrected in step S13 in the RAM 92, or if the coordinates of the pixel as the density unevenness occurrence position are not stored in the RAM 92 (S8; NO), The lighting reading data is stored in the RAM 92 as it is (S14), and the operation for specifying the density unevenness occurrence position is ended.

  Therefore, according to this configuration, it is possible to specify the density unevenness occurrence positions scattered in the image data generated by reading the reading target line of the document by the light source 42 and the CCD 49. For this reason, for example, it is possible to appropriately specify a pixel to be subjected to a correction process that reduces the appearance of density unevenness, for example, by replacing pixel data of the specified density unevenness occurrence position with pixel data of surrounding pixels. become.

  Note that the predetermined number of white LEDs adjacent to the white LED to be turned on, which is turned off when specifying the density unevenness occurrence position in the density unevenness specifying unit 90, is limited to the example shown in FIG. Not the purpose. For example, as illustrated in FIG. 7, when the light source 42 includes three light emitting element groups 6, 7, and 8, when the white LEDs 61 to 64 of the light emitting element group 6 are turned on, 8 white LEDs 71 to 74 and 81 to 84 may be turned off, that is, two white LEDs adjacent to the white LEDs 61 to 64 to be turned on may be turned off. You may change suitably the predetermined number of white LED adjacent to LED. Moreover, according to the said change, you may change suitably said 1st threshold difference value and 2nd threshold difference value.

  In addition to the above-described configuration, the image reading circuit 9 is provided with a document type receiving unit that receives an input of a document type from the operation unit 36, and the density unevenness specifying unit 90 is received by the document type receiving unit. Only when the type of the original is the original, the above-described processing for specifying the density unevenness occurrence position may be performed.

  According to this configuration, it is possible to specify the density unevenness occurrence position that occurs in the binding portion of the original that has a non-planar original surface, which is suitable for reading the original.

  In the above embodiment, a multifunction peripheral is described as an example of an image forming apparatus. However, the present invention is not limited to this, and a printer, a copier, a scanner, a FAX, or the like provided with the image reading apparatus according to the present invention is not limited thereto. It may be an image forming apparatus.

  In the above embodiment, the configurations and settings shown in FIGS. 1 to 9 are merely examples, and the present invention is not limited to the embodiment.

1 MFP (image forming device)
4 Image reading unit (image reading device)
5 Document feeder (image reading device)
9 Image reading circuit (image reading device)
25 Image forming unit 36 Operation unit (image reading device)
42 Light source (light source part)
49 CCD (light receiving unit)
61-64, 71-74 White LED (light emitting element)
90 Density unevenness specifying unit 94 Light source control unit 97 A / D conversion unit (light receiving unit)
411 Contact glass (original platen)

Claims (3)

A document table for placing a document;
A light source unit that includes a plurality of light emitting elements arranged in a main scanning direction, and that irradiates a document placed on the document table with lighting light of the plurality of light emitting elements;
The reflected light reflected from the original when the lighting light is irradiated by the light source unit to the reading target line which is one line in the main scanning direction of the original to be read in the original, and the received reflected light is received. A light receiving unit that converts the image data of the line to be read;
A light source controller that controls turning on and off of the plurality of light emitting elements;
When all the plurality of light emitting elements are turned on by the light source control unit, all lighting read data that is the image data of the reading target line converted by the light receiving unit, and the light source control unit that is turned on Each of the main scanning directions in the thinning-on reading data which is the image data of the reading target line converted by the light receiving unit when a predetermined number of the light emitting elements adjacent to the light emitting elements are turned off. A difference between pixel data is calculated, and when the difference value larger than a predetermined first threshold difference value exists among the calculated difference values, a predetermined value smaller than the first threshold difference value is determined. The pixel data corresponding to the difference value smaller than the second threshold difference value and the image indicated by the pixel data corresponding to the difference value larger than the first threshold difference value And uneven density specifying unit configured to specify a density unevenness occurring position in the reading target line,
An image reading apparatus comprising: A document type receiving unit that receives an input of the document type;
The image reading apparatus according to claim 1, wherein the density unevenness specifying unit performs the process of specifying the density unevenness occurrence position only when the document type received by the document type receiving unit is a main document. The image reading apparatus according to claim 1 or 2,
An image forming unit that forms an image on a recording medium based on an image signal obtained by a reading operation of the image reading device;
An image forming apparatus comprising:

Images